Rifles and other firearms often employ telescopic sights or riflescopes to assist a shooter in aiming and hitting targets. Because a bullet's trajectory is an arc rather than a flat line, many riflescopes incorporate a means to mechanically change or adjust the elevation, so that the resulting reticle or aiming point setting coincides with a given point in a bullet's trajectory, for a given distance or range. Thus, the shooter's point of aim coincides with the bullet's point of impact. To achieve this coincidence, the shooter must know the bullet's trajectory at each distance he intends to fire, or carry such trajectory data in the field, interpret how he must calibrate this data to the increments of his elevation, manually apply this data by setting or resetting the riflescope's elevation, and only then reacquire his target in the scope's field of view and take a well-aimed shot. To do this, the shooter must have an extensive knowledge of ballistics and must understand the degree to which his incremental elevation adjustments affect his point of impact at any distance. Unfortunately, these steps often cause shooters to lose sight of the target while resetting the scope's elevation for the required distance. Further, because the elevation knob or turret presents its numerical settings in small print, a shooter can have difficulty seeing any particular setting under ideal lighting, and cannot see the settings at all in darkness. Likewise, a riflescope's horizontal or windage adjustments to compensate for the effects of wind or target movement are confusing and too easily incorrect.